The code we have seen so far blocks the execution of the program until the resource is available. The call responsible for the waiting is time.sleep. To make the code start working on other tasks, we need to find a way to avoid blocking the program flow so that the rest of the program can go on with the other tasks.
One of the simplest ways to accomplish this behavior is through callbacks. The strategy is quite similar to what we do when we request a cab.
Imagine that you are at a restaurant and you've had a few drinks. It's raining outside, and you'd rather not take the bus; therefore, you request a taxi and ask them to call when they're outside so that you can come out, and you don't have to wait in the rain.
What you did in this ...
